Finite momentum Cooper pairing in 3D topological insulator Josephson junctions

TL;DR

This paper demonstrates finite momentum Cooper pairing in a 3D topological insulator Josephson junction, evidenced by anomalous Fraunhofer patterns caused by magnetic fields, revealing interplay between Zeeman effect and Aharonov-Bohm flux.

Contribution

It provides experimental evidence and theoretical understanding of finite momentum pairing in topological insulator Josephson junctions under magnetic fields.

Findings

Anomalous Fraunhofer patterns indicate oscillating superconducting order parameter.

Finite momentum pairing arises from Zeeman effect and Aharonov-Bohm flux.

Experimental data agrees with simulations explaining the microscopic origin.

Abstract

Unconventional superconductivity arising from the interplay between strong spin-orbit coupling and magnetism is an intensive area of research. One form of unconventional superconductivity arises when Cooper pairs subjected to a magnetic exchange coupling acquire a finite momentum. Here, we report on a signature of finite momentum Cooper pairing in the 3D topological insulator Bi2Se3. We apply in-plane and out-of-plane magnetic fields to proximity-coupled Bi2Se3 and find that the in-plane field creates a spatially oscillating superconducting order parameter in the junction as evidenced by the emergence of an anomalous Fraunhofer pattern. We describe how the anomalous Fraunhofer patterns evolve for different device parameters, and we use this to understand the microscopic origin of the oscillating order parameter. The agreement between the experimental data and simulations shows that the finite momentum pairing originates from the coexistence of the Zeeman effect and Aharonov-Bohm flux.